System and method for subscribing for internet protocol multimedia subsystems (IMS) services registration status

ABSTRACT

A system and method that allows mobile device applications to receive changes in registration status from application services that are accessed via an Internet Protocol Multimedia Subsystem (IMS). Applications on a mobile device subscribe to receive notifications of changes in registration status for requested services. When a change to the registration status of a service occurs, a notification message is transmitted to the application on the mobile device. Notifications of changes in status are thereby received by each application on a per-application-service basis. In some embodiments, when a request to register with an application service fails, the corresponding notification message includes a reason for the failure. In some embodiments, notification messages are originated by a registration manager that operates in the IMS and transmitted to an IMS client operating on a mobile device. In some embodiments, notification messages are originated by each application service and transmitted directly to subscribed applications.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/109,849, entitled SYSTEM AND METHOD FOR SUBSCRIBING FOR INTERNETPROTOCOL MULTIMEDIA SUBSYSTEMS (IMS) APPLICATION SERVICES REGISTRATIONSTATUS, filed Dec. 17, 2013, now U.S. Pat. No. 9,008,650; which is acontinuation of U.S. patent application Ser. No. 13/403,931, entitledSYSTEM AND METHOD FOR SUBSCRIBING FOR INTERNET PROTOCOL MULTIMEDIASUBSYSTEMS (IMS) APPLICATION SERVICES REGISTRATION STATUS, filed Feb.23, 2012, now U.S. Pat. No. 8,611,890; which claims the benefit of U.S.Provisional Application No. 61/445,958, entitled SUBSCRIBING FORINTERNET PROTOCOL MEDIA SUBSYSTEMS (IMS) SERVICES REGISTRATION STATUS,filed Feb. 23, 2011, the entireties of both which are herebyincorporated by reference.

BACKGROUND

The Internet Protocol Multimedia Subsystem (“IMS”) is an architecturalframework for delivering Internet Protocol (“IP”) multimedia to mobileusers, such as users of mobile devices like smart phones or tabletcomputers. An IMS core network (“IMS core”) permits wireless andwireline devices to access multimedia, messaging, and voice applicationsand services. IMS standards and specifications have been promulgated bythe 3rd Generation Partnership Project (“3GPP”™). To allow the IMS coreto be integrated with Internet resources, the 3GPP specifications useInternet Engineering Task Force protocols within the IMS core, such asSession Initiation Protocol (“SIP”) and Diameter. SIP is a signalingprotocol used for creating, modifying and terminating two-party ormultiparty sessions consisting of one or several media streams. A mobiledevice registers its IP address with a SIP registrar server within anIMS core by generating and sending a SIP request message with a“REGISTER” method token. Once registered, a mobile device maysubsequently establish multimedia sessions via the IMS core.

An IMS client (or IMS stack) software component on a mobile deviceallows one or more applications on the mobile device to register forvarious application services that are available on the IMS network. Ifthe registration is successful, the mobile device application may thentake advantage of the functionality offered by the application serviceto which it is registered. If the registration is unsuccessful, however,then the application will be unable to take advantage of the offeredfunctionality. In cases where a requested registration fails, therequesting application may benefit from receiving a notification of thefailure. In current systems, the requesting application may receive ageneric notification that alerts the mobile device only that one or moreregistration failures have occurred—without providing an indication asto which specific service registration failed. This shortcoming leads tosituations where one rejected application service triggersderegistration of all applications—even those applications that are notnecessarily supposed to terminate. Moreover, in current systems, thegeneric notification may omit information describing the nature of orreason for the failure. The lack of information conveyed to theapplication on the mobile device means that it is unable to effectivelyassess what additional steps, if any, it should take in order registerwith the application service.

FIGS. 1A and 1B offer high level illustrations of the IMS applicationservice registration procedure according to current systems. In FIG. 1A,Application 1 sends to the IMS client a request to register for anapplication service identified as ICSI_1 (step 1); Application 2 sendsto the IMS client a request to register for an application serviceidentified as ICSI_2 (step 2); and Application 3 sends to the IMS clienta request to register for an application service identified as ICSI_3(step 3). After receiving the service registration requests, the IMSclient transmits all of the received registration requests to the IMSnetwork (step 4), which returns an acknowledgement message to the IMSclient (step 5). In step 6, the IMS network sends a registration requestfor the application service identified as ICSI_3 to Application Server 3(which is associated with ICSI_3); in step 7, the IMS network sends aregistration request for the application service identified as ICSI_2 toApplication Server 2 (which is associated with ICSI_2); and, in step 8,the IMS network sends a registration request for the application serviceidentified as ICSI_1 to Application Server 1 (which is associated withICSI_1). After the IMS network sends each registration request to itsassociated application server, each respective application serverreturns to the IMS network an acknowledgment that indicates whether theregistration succeeded or failed. For example, in step 9, ApplicationServer 3 returns an “OK” acknowledgment to inform the IMS network thatthe registration succeeded; in step 10, Application Server 2 returns an“OK” acknowledgment to inform the IMS network that the registrationsucceeded; and, in step 11, Application Server 1 returns an “OK”acknowledgement to inform the IMS network that the registrationsucceeded.

Accordingly, FIG. 1A illustrates a successful registration flow in whicheach requested registration succeeded for each requested service. Inpractice, however, one or more requested registrations may fail. Forexample, FIG. 1B illustrates a registration flow identical to FIG. 1Awith the exception that, in step 9, Application Server 3 returns a “NOK”acknowledgement. Unlike the “OK” acknowledgement in step 9 of FIG. 1A,the “NOK” acknowledgement in step 9 of FIG. 1B indicates that theregistration for the application service identified as ICSI_3 hasfailed.

When such a failure occurs, the application that requested theregistration may benefit from receiving a notification that the failureoccurred. Accordingly, an application may subscribe to receivenotifications indicating whether a requested registration is successfulor unsuccessful. In practice, a single application may requestregistrations for multiple services. For example, a single applicationmay request a registration to Service A, which ultimately succeeds; mayrequest a registration to Service B, which ultimately succeeds; and mayrequest a registration to Service C, which ultimately fails. In currentsystems, the application would be notified only that a failure wasreceived; the application would not be notified as to which particularapplication service failed. In other words, the application would knowthat at least one application service failed, but the application wouldnot know whether the failure occurred with respect to Service A, ServiceB, or Service C. As a result, the application would be forced toterminate all application services (i.e., the application wouldterminate Service A, Service B, and Service C) rather than terminatingonly the one service that failed (i.e., Service C). Moreover, in currentsystems, the application receives no reason for the failure. Forexample, the application does not know whether the requestedregistration failed because the mobile device user has not paid foraccess to the failed service, because a physical connection could not beestablished to the server associated with the requested service, or fora host of possible other reasons.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a flow diagram illustrating a successful registration for IMSservices.

FIG. 1B is a flow diagram illustrating an unsuccessful registration forIMS services.

FIG. 2A is a diagram of a representative Internet Protocol MultimediaSubsystem (IMS) environment in which application services may besubscribed to by mobile devices.

FIG. 2B is a block diagram of components in a mobile device that enablereceipt of notifications of changes in registration status on aper-application basis.

FIG. 3A is a block diagram illustrating a simplified view of thedelivery of application services to mobile devices.

FIG. 3B is a block diagram of components of a Call Session ControlFunction (CSCF) network node that provides notifications of changes inregistration status on a per-application basis.

FIG. 4 is a flow diagram illustrating a partially unsuccessfulregistration for IMS services.

FIG. 5 is a flow diagram illustrating a successful registration for IMSservices in which each requesting application receives a registrationstatus notification from an IMS client.

FIG. 6 is a flow diagram illustrating a partially unsuccessfulregistration for IMS services in which each requesting applicationreceives a registration status notification from an associatedapplication service.

FIG. 7 is a block diagram illustrating the relationship betweenRegistration State Machines, Per-Application Registration StateMachines, and Per-Service Registration State Machines.

FIG. 8 is an example of an XML document that provides details of aregistration status to an application.

FIG. 9 is a block diagram illustrating a Registration State Machine anda Per-Application Registration State Machine.

DETAILED DESCRIPTION

A system and method that allows mobile device applications to receivechanges in registration status from application services that areaccessed via an Internet Protocol Multimedia Subsystem (IMS) isdisclosed herein. Applications on a mobile device transmit a request toregister with one or more application services available via the IMSnetwork. The applications on the mobile device subscribe to receivenotifications of changes in registration status for the one or morerequested services. When a change to the registration status of aservice occurs—particularly a termination of a service—a notificationmessage is transmitted to the application on the mobile device. Byreceiving notifications of changes in status on aper-application-service basis, applications in the mobile device arebetter able to assess what remedial steps, if any, may be taken tore-subscribe to the application service, locate a different applicationservice, or halt or otherwise adjust the operation of the currentapplication in the event of a registration failure.

In some embodiments, when a request to register with an applicationservice fails, the corresponding notification message includes a reasonfor the failure. The reason for the failure may be transmitted to themobile device in, for example, an extensible markup language (XML)document. The reason for the failure provides additional information toassist applications on the mobile device to determine what, if any,remedial steps should be taken. In some embodiments, the notificationmessage extends the Subscription to Registration Information defined bythe Internet Engineering Task Force (IETF) in a Request for Comments(RFC). In one example, IMS Communication Service Identifiers (ICSIs) andIMS Application Registry Identifiers (IARIs) are used to communicate thestatus of individual services.

In some embodiments, notification messages are originated by aregistration manager that operates in the IMS. The registration managertransmits notification messages to an IMS client operating on a mobiledevice, where the contents of the messages are distributed to thesubscribed applications on the mobile device. In some embodiments,notification messages are originated by each application service andtransmitted directly to subscribed applications on a mobile device.

Various embodiments of the invention will now be described. Thefollowing description provides specific details for a thoroughunderstanding and an enabling description of these embodiments. Oneskilled in the art will understand, however, that the invention may bepracticed without many of these details. Additionally, some well-knownstructures or functions may not be shown or described in detail, so asto avoid unnecessarily obscuring the relevant description of the variousembodiments. The terminology used in the description presented below isintended to be interpreted in its broadest reasonable manner, eventhough it is being used in conjunction with a detailed description ofcertain specific embodiments of the invention.

Representative Environment

FIG. 2A is a diagram of a representative Internet Protocol MultimediaSubsystem (IMS) environment 200 in which notification messages fromapplication services reflecting changes in registration status arecommunicated to mobile devices. In the environment 200, mobile devices202 are configured to communicate with, or through, a trusted radioaccess network (“RAN”) 204 and/or an untrusted RAN 203, in order toregister with and utilize an IMS core 207. The IMS allows serviceproviders to implement a compelling set of mobile services for mobiledevices. IMS registration for different IMS services may be based on SIPEvent Package for Registration Information defined in Request forComments (RFC) 3680 and procedures defined in 3GPP Test Specification(TS) 24.229.

Users may employ mobile devices 202 to communicate with other users anddevices. In addition, users may employ mobile devices 202 to receive,provide, or otherwise interact with multiple IMS services. For example,location-based services are services that use the actual or approximatelocation of a mobile device to provide, enhance, or supplement a serviceto the mobile device. Location-based services include, but are notlimited to, services such as emergency services (e.g., E911), assettracking or recovery services (e.g., the tracking of a stolen car),location-based alerts or advertising services (e.g., targetedadvertisements that depend on the location of a mobile device user),social networking services (e.g., services that report the relativelocation of friends or family), and/or the like. In addition, users mayemploy mobile devices 202 to receive, provide, or otherwise interactwith additional IMS services, including image sharing services, gamingservices, multimedia telephony services, instant messaging and presenceservices, video conferencing and sharing services, Push-to-talk overCellular (PoC) services, 3GPP combinational services (CSI), and othertelecommunications and Internet converged services. Once a mobile device202 has successfully registered with the IMS core 207, the device mayestablish multimedia sessions managed by the IMS core in order to accessapplications and services that facilitate communication, location-basedservices and/or other services.

Mobile devices 202 may include virtually any devices for communicatingover a wireless network. Such devices include mobile telephones, such asGlobal System for Mobile Communications (“GSM”) telephones, TimeDivision Multiple Access (“TDMA”) telephones, Universal MobileTelecommunications System (“UMTS”) telephones, Evolution-Data Optimized(“EVDO”) telephones, Long Term Evolution (“LTE”) telephones, GenericAccess Network (“GAN”) telephones, Unlicensed Mobile Access (“UMA”)telephones, and other mobile computers or devices, such as Voice overInternet Protocol (“VoIP”) devices, Secure User Plane Location (“SUPL”)Enabled Terminals (SETs), Personal Digital Assistants (“PDAs”), radiofrequency devices, infrared devices, handheld computers, laptopcomputers, wearable computers, tablet computers, pagers, integrateddevices combining one or more of the preceding devices, and/or the like.

As shown in FIG. 2B, which is a block diagram of a representative mobiledevice, each mobile device 202 typically includes a processor 270 forexecuting processing instructions, a data storage medium component 280(e.g., hard drive, flash memory, memory card, etc.), volatile memoryand/or nonvolatile memory 290, a power supply 300, one or more networkinterfaces (e.g., Bluetooth Interface 250; and Network CommunicationInterface 255, which enables the mobile phone to communicate bytransmitting and receiving wireless signals using licensed,semi-licensed or unlicensed spectrum over a telecommunications network),an audio interface 285, a display 260, a keypad or keyboard 265, andother input and/or output interfaces 295. The various components of amobile device may be interconnected via a bus. The volatile andnonvolatile memories generally include storage media for storinginformation such as processor-readable instructions, data structures,program modules, or other data. Some examples of information that may bestored include basic input/output systems (BIOS), operating systems, andapplications. The stored information may include one or more SIP clientscapable of generating, transmitting and interpreting syntacticallycorrect SIP messages. SIP clients permit the mobile device to registerwith and communicate via the ISM core 207.

Returning to FIG. 2A, mobile devices 202 may connect to the IMS core 207by a trusted RAN 204 or an untrusted RAN 203. Both types of RANs providea first physical wireless link between mobile devices 202 and the IMScore. A single mobile device may be capable of using one or both typesof RANs. The RANs 203, 204 may use any wireless communications and dataprotocol or standard, such as GSM, TDMA, UMTS, EVDO, LTE, GAN, UMA, CodeDivision Multiple Access (“CDMA”) protocols (including IS-95, IS-2000,and IS-856 protocols), Advanced LTE or LTE+, Orthogonal FrequencyDivision Multiple Access (“OFDM”), General Packet Radio Service(“GPRS”), Enhanced Data GSM Environment (“EDGE”), Advanced Mobile PhoneSystem (“AMPS”), WiMAX protocols (including IEEE 802.16e-2005 and IEEE802.16m protocols), Wireless Fidelity (“WiFi”), High Speed Packet Access(“HSPA”), (including High Speed Downlink Packet Access (“HSDPA”) andHigh Speed Uplink Packet Access (“HSUPA”)), Ultra Mobile Broadband(“UMB”), SUPL, and/or the like.

The trusted RAN 204 is a RAN operated by the operator of the IMS core207 or another trusted party that is associated with the IMS coreoperator (e.g., the operator's contractor, affiliate, or industrypartner). In order to wirelessly communicate via the trusted RAN, amobile device 202 may need to pass preliminaryauthentication/authorization checks implemented in part by the trustedRAN. The trusted RAN is connected to and communicates with the IMS corevia a dedicated backhaul (e.g., a private network that is not open tothe public) and intermediary components 206. The intermediary componentsmay include, for example, a Gateway GPRS Support Node (“GGSN”), ServingGPRS Support Node (“SGSN”) or similar components that facilitatemobility management, session management, and transport for IP packetservices within the trusted RAN 204.

The untrusted RAN 203 is a RAN that connects to the IMS core 207 over apublic network such as the Internet. The untrusted RAN may not implementauthentication/authorization tests sufficient to prevent securityattacks upon the IMS core. In some examples, a mobile device 202 uses aWiFi, GAN, or UMA protocol to connect to an untrusted RAN at a wirelessaccess point.

The intermediary components 206 and the untrusted RAN 103 are bothconnected to the IMS core 207. The IMS core comprises various CallSession Control Functions (“CSCF”) and other components that, interalia, provide SIP registrar and proxy functionality. The IMS corecomprises a proxy CSCF (“P-CSCF”) 208, an interrogating CSCF (“I-CSCF”)212, a serving CSCF (“S-CSCF”) 216, a Security Gateway (“SEG”)/SessionBorder Controller (“SBC”) 210, and a Home Subscriber Server (“HSS”) 214.The basic functionalities of the IMS core components are described bystandards promulgated by the 3GPP, including 3GPP TS 23.002, version9.2.0 Release 9, which is hereby incorporated by reference in itsentirety.

As shown in FIG. 2A, the intermediary components 206 connect the trustedRAN 204 to the IMS core 207 via the P-CSCF 208. In contrast, theuntrusted network 203 connects to the P-CSCF 208 indirectly via theSEG/SBC 210. The SEG/SBC may establish a secure IP tunnel between amobile device 202 and the IMS core. In some examples, a trusted network204 may connect to the P-CSCF via the SEG/SBC. In other examples, theuntrusted network may directly connect to the P-CSCF via the Internet.

In order to register with the IMS core 207, a SIP client running on amobile device 202 generates and sends an initial SIP registrationmessage to the IMS core via the trusted RAN 204 or untrusted RAN 203.The initial registration message comprises a REGISTER method token andextended header information, including an IMEI and IMSI associated withthe mobile device 202. The P-CSCF 208 receives the initial SIPregistration message and forwards the message to the I-CSCF 212. Oneskilled in the art will appreciate that in some examples, the P-CSCF mayalso perform some or all of the functionality of the SEG/SBC 210.

The I-CSCF 212 and/or S-CSCF 216 may utilize the IMEI/IMSI identifiersin the received registration message to generate and send a userauthorization request (“UAR”) to the HSS 214 via the Diameter protocol.The UAR includes, inter alia, the IMEI and IMSI associated with themobile device 202. In some examples, the I-CSCF utilizes the SIPregistration message forwarded from the P-CSCF to generate and send theUAR to the HSS and the S-CSCF implements additional standard IMSregistration methods. In other examples, the I-CSCF does not generateand send the UAR, but instead queries the HSS to identify which S-CSCFto forward the registration message to. In such examples, the I-CSCFthen forwards the received SIP registration message to the identifiedS-CSCF. As described in greater detail herein, the S-CSCF then utilizesthe SIP registration message to generate and send the UAR to the HSS.The S-CSCF may send the SIP registration message to one or moreapplication servers 220, 225, and 230 in order to complete theregistration process. The S-CSCF also implements additional standard IMSregistration methods (e.g., HTTP digest or Authentication and KeyAgreement (“AKA”) authentication).

The HSS 214 is a master user database that contains subscription-relatedinformation such as subscriber profiles. The HSS performs authenticationand authorization of a mobile device 202 and provides information abouta mobile device's IP address. The HSS may perform standard IMSregistration processes as described by 3GPP specifications andstandards. The HSS also validates the IMEI/IMSI identifiers in the UARin order to determine whether to deny registration to a mobile device202. The HSS may also use a received IMEI to determine the capabilitiesof a mobile device.

Overview of Registration with IMS Services

FIG. 3A is a block diagram providing a simplified view of theregistration and delivery of IMS application services to mobile devices.Applications running in the mobile device 305 use an IMS client 325 toregister for application services in the IMS network. The IMS client (orIMS stack) maintains an IMS registration as long as an application needsto stay connected with a corresponding application service. The IMSproxies (*-CSCFs) 330 in the IMS network maintain the registrationinitiated by the mobile device and provide the appropriate routing forIMS traffic. When for any reason one of the application servers involvedrejects the initial registration request, the IMS service is notavailable to the mobile device and the application functionality on themobile device may be substantially or completely impacted by theregistration failure.

In FIG. 3A, three applications on the mobile device 305 are depicted asusing applications services, namely application A (310), application B(315), and application N (320). Applications on the mobile devicecommunicate with the IMS network through IMS client 325. The IMS client325 resides within the mobile device and manages communications betweenmobile device applications and other components in the IMS network. Forexample, IMS client 325 receives registration requests from the mobiledevice applications (310, 315, and 320), forwards the receivedregistration requests to IMS network 370, receives registration statusnotification subscription requests from the mobile device applications,and forwards the received registration status notification subscriptionrequests to the IMS network. In some embodiments, the IMS client 325additionally receives registration status notifications from theapplication services 340, 350, and 360 and forwards the received statusnotifications to the appropriate mobile device applications. Thoseskilled in the art will appreciate that the IMS client 325 may beimplemented in an Android™, Windows™, iOS™, or other operating systemenvironment that is used by mobile devices.

The IMS client 325 connects to a registration manager component 335within one or more of the CSCF 330 in the IMS network. The registrationmanager component 335 resides within the IMS network and managesregistrations between one or more mobile device applications 310, 315,and 320 and one or more application services 340, 350, and 360. Forexample, registration manager 335 receives registration requests fromthe mobile device applications, forwards the received registrationrequests to the appropriate application servers, receives registrationstatus notification subscription requests from the IMS client, andforwards the received registration status notification subscriptionrequests to the appropriate application servers. In some embodiments,registration manager 335 may receive a single request that functions asboth a registration request and a registration status notificationsubscription request. After receiving the request, registration manager335 may forward the request to the appropriate application service andautomatically subscribe the application to receive status notificationsassociated with that service. In some embodiments, registration manager335 additionally receives registration status notifications from one ormore application servers and forwards the received registration statusnotifications to the IMS client 325.

FIG. 3B is a block diagram of a CSCF 330 node within IMS network 370which implements the functionality of the registration manager component335. The CSCF 330 may contain one or more processors 375 for executingprocessing instructions, a data storage medium component 385 (e.g., harddrive, flash memory, memory card, etc.), and volatile memory and/ornonvolatile memory 380. Instructions for implementing functions of theregistration manager 335 may be stored in the data storage medium and/ormemory and executed by the processor. While the registration managercomponent 335 functionality is depicted as residing within the CSCF 330in FIG. 3B, it will be appreciated that the registration managercomponent 335 may be implemented independently from the CSCF 330. Thatis, the registration manager component 335 may be operated as astand-alone service within the IMS network 370 or may be incorporated inother network nodes within the IMS network 370.

Returning to FIG. 3A, IMS network 370 may be connected to multipleapplication servers which provide application services. For example,registration manager 335 may connect to a status notification component345 within application service A, to status notification component 355within application service B, and to status notification component 365within application service N. Each status notification component (345,355, 365) resides within its respective application service, managescommunications between its respective application servers and the IMSnetwork, and processes the registration request (i.e., enables an activeconnection between the application that initiated the registrationrequest and the application server on which the requested serviceresides). For example, the status notification component 355 receives aregistration request from the IMS network, processes the requestedregistration, and generates a registration status notification thatindicates whether the requested registration was successful orunsuccessful. In one embodiment, the status notification component 355sends the generated notification to the IMS network, which may thenforward the generated notification to the requesting application. Inanother embodiment, the status notification component 355 sends thegenerated notification directly to the application that requested theregistration to the service. In FIG. 3A, the three services areindependent of each other, i.e., the value provided by applicationservice A does not depend on application service B or applicationservice C being available. Moreover, service A will remain availableeven if access to service B is not granted or otherwise terminates forany reason.

Registration to IMS Services and Subscription to RegistrationInformation

FIG. 4 is a flow diagram illustrating a partially unsuccessfulregistration for IMS services. Application A connects to the IMS client(step 1), which requests a registration to the IMS network (step 2). TheIMS network authenticates the mobile device on which the requestingapplication resides and sends to the IMS client an indication of whetherthe IMS network registration was successful or unsuccessful. Forexample, in step 3, the IMS network returns a “200 OK” status to the IMSclient, thereby indicating that the registration to the IMS networksucceeded. In step 4, the IMS client forwards the successful statusindication to Application A. In step 5, after receiving the registrationrequest, the IMS network forwards the registration request (originatingfrom Application A) to Application Service A. Application Service A mayreturn to the IMS network an indication of whether the applicationservice registration was successful or unsuccessful. For example, atstep 6, Application Service A returns a “200 OK” status to the IMSnetwork, thereby indicating that the registration to Application ServiceA succeeded.

Next, Application B connects to the IMS client (step 7) to request aregistration to the IMS network (step 8). Because the mobile device onwhich Application B resides was previously connected to the IMS network(in step 2), the connection is simply refreshed rather thanreestablished (step 8). The IMS network then sends to the IMS client anindication of whether the IMS network refresh was successful orunsuccessful. For example, in step 9, the IMS network returns a “200 OK”status to the IMS client, thereby indicating that the registration(i.e., the refresh) to the IMS network succeeded. In step 10, the IMSclient forwards the successful status indication to Application B. Instep 11, after receiving the registration request, the IMS networkforwards the registration request (originating from Application B) toApplication Service B. Application Service B may return to the IMSnetwork an indication of whether the application service registrationwas successful or unsuccessful. For example, at step 12, ApplicationService B returns a “200 NOK” status to the IMS network, therebyindicating that the registration to Application Service B failed.

In order to be made aware of any failed registration requests,Application A may request a subscription to receive notificationsregarding any requested connections. For example, in step 13,Application A sends a subscription request to the IMS client. In step14, the IMS client forwards the subscription request to the IMS network.The IMS network then sends to the IMS client an indication of whetherthe subscription to receive notifications was successful orunsuccessful. For example, the IMS network returns a “200 OK”confirmation to the IMS client (step 14.1), which then forwards theconfirmation to Application A (step 14.2).

In step 15, the IMS network sends notification information to the IMSclient. The IMS client acknowledges receipt of the notification (step16.1) and forwards the received notification to Application A (step16.2) because Application A previously subscribed to receivenotifications (step 13).

In step 17, Application B sends a subscription request to the IMSclient. In step 18, the IMS client forwards the subscription request tothe IMS network. The IMS network then sends to the IMS client anindication of whether the subscription to receive notifications wassuccessful or unsuccessful. For example, the IMS network returns a “200OK” confirmation to the IMS client (step 18.1), which then forwards theconfirmation to Application B (step 18.2).

In step 19, the IMS network sends notification information to the IMSclient. The IMS client acknowledges receipt of the notification (step19.1) and forwards the received notification to Application B (step 20)because Application B previously subscribed to receive notifications(step 17). In addition, the IMS client forwards the receivednotification to Application A (step 20.1) because Application A alsopreviously subscribed to receive notifications (step 13). Thenotification information provides an indication of the status of theservices to each application on a per-service basis. Providingnotification information to the applications allows the applications tobetter determine what actions to take when the status of an applicationservice changes.

FIG. 5 is a flow diagram illustrating a successful registration for IMSservices in which each requesting application receives a registrationstatus notification from the IMS client 325. Application 1 sends to theIMS client a request to register for a service identified as ICSI_1(step 1); Application 2 sends to the IMS client a request to registerfor a service identified as ICSI_2 (step 2); and Application 3 sends tothe IMS client a request to register for a service identified as ICSI_3(step 3). After receiving the service registration requests, the IMSclient sends all of the received requests to the IMS network (step 4),which returns an acknowledgement message to the IMS client (step 5). Instep 6, the IMS network sends a registration request for the serviceidentified as ICSI_3 to Application Service 3 (which is associated withICSI_3); in step 7, the IMS network sends a registration request for theservice identified as ICSI_2 to Application Service 2 (which isassociated with ICSI_2); and, in step 9, the IMS network sends aregistration request for the service identified as ICSI_1 to ApplicationService 1 (which is associated with ICSI_1). At step 8, the IMS networkreceives from the IMS client a subscription request to receivenotification information regarding all registration requests sent by theIMS client. At step 10, the IMS network sends to the IMS client anacknowledgement of the request. After the IMS client is successfullysubscribed to receive notifications, the IMS network receivesregistration status from each service for which a registration has beenrequested: in step 11, Application Service 3 sends a “NOK”acknowledgment to inform the IMS network that the registration failed;in step 12, Application Service 2 returns an “OK” acknowledgment toinform the IMS network that the registration succeeded; and, in step 13,Application Service 1 returns an “OK” acknowledgement to inform the IMSnetwork that the registration succeeded. After receiving registrationstatus for each service, the IMS network sends a notification to the IMSclient (step 14), which returns an acknowledgment to the IMS network(step 15). After receiving the notification from the IMS network, theIMS client forwards the received notification to all applicationsconnected to the IMS client: at step 16, the IMS client forwards thereceived notification to Application 3; at step 17, the IMS clientforwards the received notification to Application 2; and, at step 18,the IMS client forwards the received notification to Application 1.

FIG. 6 is a flow diagram illustrating a partially unsuccessfulregistration for IMS services in which each requesting applicationreceives a registration status notification directly from an associatedapplication service. Application 1 sends to the IMS client a request toregister for a service identified as ICSI_1 (step 1); Application 2sends to the IMS client a request to register for a service identifiedas ICSI_2 (step 2); and Application 3 sends to the IMS client a requestto register for a service identified as ICSI_3 (step 3). After receivingthe service registration requests, the IMS client sends all of thereceived requests to the IMS network (step 4), which returns anacknowledgement message to the IMS client (step 5). In step 6, the IMSnetwork sends a registration request for the service identified asICSI_3 to Application Service 3 (which is associated with ICSI_3); instep 7, the IMS network sends a registration request for the serviceidentified as ICSI_2 to Application Service 2 (which is associated withICSI_2); and, in step 8, the IMS network sends a registration requestfor the service identified as ICSI_1 to Application Service 1 (which isassociated with ICSI_1). At step 9, the IMS client receives fromApplication 1 a subscription request to receive notification informationregarding all registration requests sent by application 1. At step 10,the IMS client forwards the subscription request to the IMS network,and, at step 11, the IMS network forwards the subscription request toApplication Service 1. After receiving the subscription request,Application Service 1 returns an acknowledgement directly to Application1 (step 12). At step 13, Application Service 1 sends a notification toApplication 1, which returns an acknowledgement to Application Service 1(step 14).

Registration State Machines and Per-Application Registration StateMachines

FIG. 9 depicts a Registration State Machine (RSM) that is associatedwith each mobile device registered with the IMS core. As outlined in RFC3680, an RSM 100 is associated with each mobile device address ofrecord. When no mobile device is registered for the address of record,the RSM is in “Init” state 105. The RSM transitions to “Active” state110 when a mobile device is registered to the address of record. The RSMstays in the Active state as long as there the mobile device isregistered. When the mobile device is de-registered, the RSM transitionsto “Terminated” state 115 and then immediately transitions to Init state105. The transition from the Init state to the Active state, and thetransition from the Active state to the Terminated state, generates anotification to any subscriber for registration information. Thetransition from the Terminated state to the Init state does not generatea notification.

FIG. 9 also depicts a per-application Registration State Machine 125that is associated with each mobile device application making servicecalls through the IMS core. Each mobile device registration isassociated with a set of applications. In addition to RSM 100 associatedwith the mobile device, each application on the mobile device is alsomodeled with its own state machine (a “per-application RSM”). However,per-application RSMs 125 do not exist when no application is registered.By contrast, RSM 100 always exists whenever an address of record exists.The Init state 130 and the Terminated state 140 of per-applications RSMsare transient, i.e., per-application RSMs transition to Active state 135immediately after creation. When Terminated, per-application RSMstransition to Destroyed state 145. Consequently, subscribers are notnotified regarding transitions from the Init state to the Active stateand from the Terminated state to the Destroyed state.

The registration manager 335 may send registration information to amobile device whenever the state of the RSM or any per-application RSMsis changed. In order to reduce notification traffic, the server maynotify the full state only when subscribers require such a notification.Such a required notification may occur, for example, when a Subscribewith expire timer is received. Otherwise, the notification may containonly information about the RSM that changed states.

Per-Service Registration State Machines

As previously described herein, each application on a mobile device maybe registered with a set of one or more services. These services areidentified by IMS Communication Service Identifiers (ICSIs) or IMSApplication Registry Identifiers (IARIs). Each of these services ismodeled with its own per-service Registration State Machines (a“per-service RSM”). The per-service RSM is instantiated when anapplication is registered for the IMS Service (as identified by an ICSIor IARI) and is deleted when the registration of the application for theIMS service identified by the ICSI or IARI is removed. A per-service RSMis identical to a per-application RSM, with the difference that for oneper-application RSM there can be more than one per-service RSM.

Each application service may generate notifications to subscriberswhenever an event occurs applicable to that service. In practice,however, notifications for each event at the service level may not bedesirable. For the per-service RSMs, transitions to the Active state andtransitions to the Terminated state can be notified to all subscribers.All other transitions may or may not be notified by the registrationmanager 335. Furthermore, in practice, it may be desirable to avoidgenerating full notifications that contain the entire registrationstatus. Rather, notifications may contain registration information aboutonly the changes that have actually occurred. For example, anapplication may be registered for a first service identified by ICSI-1and for a second service identified by ICSI-2, thereby resulting in twoper-service RSMs. When the RSM for ICSI-2 is terminated, thenotification will contain the registration information that describesonly this transition. The fact that the service identified by ICSI-1stays Active is not notified.

Applying the per-service RSM in this manner enables applications runningin the mobile device to subscribe to the IMS Service state and benotified only when a state change occurs. In the example above, the IMSapplication delivering the service identified by ICSI-2 can de-registerand notify the user while the application delivering the serviceidentified by ICSI-1 will continue to run.

Relationship Between RSM, Per-Application RSMs, and Per-Service RSMs

The diagram in FIG. 7 depicts the relationship between RSM 405,Per-Application RSMs 410, and Per-Service RSMs 415. When an RSM is inactive state, at least one per-application RSM must exist because anyregistration must be associated with a set of applications. However, theper-service RSM is associated with a service identified by an ICSI orIARI. In practice, applications may be registered for IMS but notregistered for a particular service.

A subscriber (i.e., an application or IMS client) may requestnotifications on transitions in the full RSM or in a per-service RSM.For the full RSM, the subscriber may send a Subscribe Request inaccordance with RFC 3680. For the per-service RSM, the subscriber mayinclude all of the ICSIs and IARIs identifying the per-service RSM inthe Subscribe Request or in a separate request. The registration manager335 accepts subscriptions to a per-service RSM and generatesnotifications representing the services identified by ICSIs and IARIsreceived in the Subscribe Request.

Registration Information Document

The registration manager 335 may convey changes in registration statusto a mobile device in a Registration Information document. FIG. 8depicts a representative Registration Information document 800,formatted as an extensible markup language (XML) document. It will beappreciated that other formatting languages may be used to provide theregistration status information other than the one depicted.

The Registration Information document is represented by a reginfoelement 805 and its version and state attribute. The RSM is representedby the Registration element 810 and its aor, id and state attributes.The per-application RSM is represented by the contact element, itsattributes (attr), and the uri element. The unknown-param element isspecially defined to convey application header parameters that are notspecified in the SIP specification document (RFC 3261). In the depicteddocument, the unknown-param element is therefore used to represent theper-service RSM. Specifically, the unknown-param element is populatedwith the ICSI and IARI parameters 815 specifying the services for whichregistration status is sought or provided. As specified in TS 24.229,ICSIs are encoded as g.3gpp.icsi-ref and IARIs are encoded asg.3gpp.iari-ref. All application identifiers and service identifiers areadded by the mobile device in the Contact and/or Accept-Contact headerduring the registration phase. These identifiers may also be included inall of the generic procedures applicable to other requests than Registerrequest.

In addition to including the registration status of identified services,the Registration Information document may also contain an element 820that conveys a reason for a per-service RSM transition. The reason maybe provided when a service transitions to the Terminated state, or maybe provided when a service transitions to other states. For example, inFIG. 8 the representative Registration Information document describes anactive RSM, an active per-service RSM for MMTEL services, and aterminated per-service RSM for GameX version 1 services. In particular,the Registration Information indicates that the GameX Service failedbecause “[the user's] Subscription to GameX services has beenterminated.” By providing such reason for the per-service transition toan application, the application is able to convey that information to auser in order to enable the user to take steps to remedy the terminationcondition. Indeed, the actual reason for the state transition isparticularly important in situations where the reason for a transitionto the Terminated state is intended to be shown to a user of the mobiledevice.

In general, the system and method disclosed herein thereby extends theper-application RSM defined in RFC 3680 and defines a per-service RSM inthe IMS context. Accordingly, the disclosed system allows an IMSapplication running in the mobile device to subscribe to state changesof a particular IMS service. It also allows an IMS Network to terminateone service while allowing others to continue.

The ability to provide registration status information on a per-servicebasis and a provide a reason for a transition to the Terminated stateenables applications to make more efficient use of system resources andprovide a richer user experience. For example, applications may make useof status and reason information to maintain service connections thathave been successfully established while reattempting services thatpreviously failed. Furthermore, registration status and reasoninformation may allow an application to inform a user as to why aparticular requested service is not available. A person of ordinaryskill will appreciate that registration status and reason informationmay allow the disclosed system to offer additional functionality thatmay provide a richer user experience, such as displaying an indicationas to whether a service interruption is temporary in nature (e.g., anapplication server is temporarily offline), or displaying an indicationthat the service interruption will remain in effect until the user takesa specified action (e.g., paying an overdue bill to the service provideror agreeing to pay for one or more individual services).

The above Detailed Description of embodiments of the system is notintended to be exhaustive or to limit the system to the precise formdisclosed above. While specific embodiments of, and examples for, thesystem are described above for illustrative purposes, various equivalentmodifications are possible within the scope of the system, as thoseskilled in the relevant art will recognize. For example, while processesor steps are presented in a given order, alternative embodiments mayperform routines having steps, or employ systems having steps, in adifferent order, and some processes or steps may be deleted, moved,added, subdivided, combined, and/or modified to provide alternative orsubcombinations. Each of these processes or steps may be implemented ina variety of different ways. Also, while processes or steps are at timesshown as being performed in series, these processes or steps may insteadbe performed in parallel, or may be performed at different times.

I claim:
 1. A computer-implemented method in a mobile device to receiveservice notifications from registered application services that areaccessed via an Internet Protocol Multimedia Subsystem (IMS), the methodcomprising: at the mobile device, requesting, via an IP multimediasubsystem (IMS), registration of at least one application on the mobiledevice with multiple associated application services; receiving, on themobile device, multiple notifications from the multiple applicationservices, wherein each of the notifications indicate, on aper-application-service basis, the status of the correspondingapplication service, wherein at least one of the notifications indicatesa failure of the corresponding application service and an indication ofa reason for the failure of the corresponding application service, andwherein each notification is received by the corresponding applicationon the mobile device for which the notification is intended; anddisplaying an indication as to whether the failure is temporary innature in response to determining that the received notificationindicates that the registration is terminated, or displaying anindication that the failure will remain in effect until a specifiedaction is taken in response to determining that the receivednotification indicates that the registration is terminated.
 2. Thecomputer-implemented method of claim 1, wherein the multiplenotifications include an indication of whether each requestedregistration is active or terminated.
 3. The computer-implemented methodof claim 1, further comprising deregistering the correspondingapplication on the mobile device if the received notification indicatesthat the registration is terminated.
 4. The computer-implemented methodof claim 1, wherein at least one application service is a location-basedservice or a multimedia telephony service.
 5. The computer-implementedmethod of claim 1, wherein at least one application service is a videoconferencing and sharing service, or an instant messaging and presenceservice.
 6. The computer-implemented method of claim 1, wherein thenature of the failure corresponds to a server that is temporarilyoffline.
 7. The computer-implemented method of claim 1, wherein thespecified action is paying an overdue bill or agreeing to pay for aservice.
 8. A computer-implemented method of providing applicationservice status notifications to mobile devices for services that areaccessed via an Internet Protocol Multimedia Subsystem (IMS), the methodcomprising: receiving, from a plurality of mobile devices, requests toreceive notifications of status changes of application services accessedby the plurality of mobile devices via an IP Multimedia Subsystem (IMS);receiving at least one notification from application services, eachnotification providing a status of a corresponding application service;identifying mobile devices that are associated with the applicationservice in each received notification; and for each receivednotification: providing the received notification to the identifiedmobile devices that are associated with the application service, whereinthe notification indicates, on a per-application-service basis, thestatus of the application service and an indication of a reason for thestatus of the application service; and in response to determining thatthe received notification indicates that the registration is terminated,providing a notification that a failure is temporary, or providing anotification of a particular action to take in order to clear a failure.9. The computer-implemented method of claim 8, wherein the receivedstatus indicates whether the requested application service is active orterminated.
 10. The computer-implemented method of claim 8, wherein atleast one application service is a location-based service or amultimedia telephony service.
 11. The computer-implemented method ofclaim 8, wherein at least one application service is a videoconferencing and sharing service, or an instant messaging and presenceservice.
 12. The computer-implemented method of claim 8, wherein thefailure results from a server that is temporarily offline.
 13. Thecomputer-implemented method of claim 8, wherein the particular action ispaying an overdue bill or paying for an additional service.
 14. Thecomputer-implemented method of claim 8, wherein the reason for thereceived status is contained in an extensible markup language (XML)document.
 15. A non-transitory computer-readable medium storinginstructions that, when executed by a processor of a mobile device,cause the mobile device to execute a method to receive changes inregistration status from application services that are accessed via anInternet Protocol Multimedia Subsystem (IMS), the method comprising:receiving, on the mobile device, a request to register at least oneapplication on the mobile device with at least one application serviceaccessed via an IP multimedia subsystem (IMS); transmitting, via theIMS, the registration request to at least one associated applicationservice; receiving, by the at least one associated application on themobile device, one or more notifications regarding the requestedregistration, the one or more notifications indicating, on aper-application-service basis, the registration status of eachapplication service and an indication of a reason for the registrationstatus of the corresponding application service; and displaying anindication as to whether a failure is temporary in nature in response todetermining that the received notification indicates a terminatedregistration, or displaying an indication that a failure will remain ineffect until a specified action is taken in response to determining thatthe received notification indicates a terminated registration.
 16. Thenon-transitory computer-readable medium of claim 15, wherein the reasonfor the registration status is contained in an extensible markuplanguage (XML) document.
 17. The non-transitory computer-readable mediumof claim 15, wherein the instructions further cause the mobile device toderegister the associated application on the mobile device in responseto determining that the received notification indicates a terminatedregistration.
 18. The non-transitory computer-readable medium of claim15, wherein at least one application service is a location-basedservice, a telephony service, or a video conferencing and sharingservice.
 19. The non-transitory computer-readable medium of claim 15,wherein the nature of the failure corresponds to a server that istemporarily offline.
 20. The non-transitory computer-readable medium ofclaim 15, wherein the specified action is paying an overdue bill oragreeing to pay for a service.